1. Industrial Useful Field
This invention relates to an improvement in a damper disc for increasing and decreasing a hysteresis torque generated in accordance with a change of torsion angle.
2. Prior Art
Utility Model No. 55-12598 has conventionally been known as a clutch or damper disc for increasing and decreasing hystersis torque. In this conventional embodiment, two friction washers 12 are mounted on spline hub 10 mounted on, therebetween. Friction plates 14 are pressed by a cone spring 15 on the external sides of friction washers 12 respectively. Projections 14a are formed on inner peripheral parts of the friction plates 14, as shown in FIG. 7 hereof. Projections 14a fit into two side plates 16 in such a manner that they can slide freely relative to each other within a specified torsion angle. A small hysteresis torque is generated by the friction plates 14 within a small torsion angle at which the side plates 16 and the friction plates 14 are slidable relative to each other. A large torsion torque is generated by the friction plates 14 and the friction washers 12 when the torsion torque becomes large.
In the above-mentioned conventional embodiment, however, a large force applied on the projection 14a lessens the strength of the projection 14a because the projection 14a is provided at the inner peripheral part of member 14. Further, since it is necessary to form a notch 16a for passing through the projection 14a on the side plate 16, a deviated wear on a contact surface between the friction plate 14 and the side plate 16 is apt to occur. A specified hysteresis torque can not be obtained if such wear occurs.
Further, in the case of the construction illustrated in FIG. 7, the small torsion angle can generate only a minimum hysteresis torque so that obtainable characteristics are limited. Therefore, in case when a comparatively large hysteresis torque of about 50% of the large torsion angle, for example, is required even in the small torsion angle range, the required hysteresis characteristics can not be obtained.
Object of the Invention
A first object of the present invention is to overcome the above-mentioned problem. A further object thereof is to make it possible to obtain a desired hysteresis characteristic by means of a difference of contact area of an intermediate member.
In order to accomplish the first object, in this invention, first friction washers generating a large hysteresis torque are provided on opposite sides of a flange of a spline hub having a spline internal tooth. An approximately annular disc-like intermediate member is provided so as to be pressed onto the outside of at least one of the friction washers. A projection projecting toward a side plate is formed on a radially outer peripheral part of the intermediate member. The projection is fitted into the side plate in such a manner that they can slide freely relative to each other within a specified torsion angle. A second friction washer generating a small hysteresis torque of provided between the intermediate member and the side plate.
In order to accomplish a desired hysteresis characteristic by means of a difference of contact area of the intermediate member, the first friction washers generating a large hysteresis torque and are provided on opposite sides of the flange of at least one hub having a spline internal tooth. An approximately annular disc-like intermediate member made of a friction material is pressed on an outside of at least one of the friction washers. A projection projecting toward a side plate is formed on a radially outer peripheral part of the intermediate member, the projection being fitted into the side plate in such a manner that the intermediate member and side plate can slide freely relatively to each other within a specified torsion angle. A first contact face having a large area is formed on a face at the first friction washer side of the intermediate member. A second contact face having a small area is formed on a face at the side plate side of the intermediate member.